Heat transfer plates

ABSTRACT

There is disclosed herein a heat transfer plate adapted to be disposed between coils of metal in an annealing furnace, the plate comprising a plurality of circumferentially spaced bars disposed in two opposing layers, the bars being skewed with respect to true radii of the plate whereby the bars of one layer partially overlap the bars of the other layer.

I Umted States Patent [1 1 [111 3,802,834 Corbett, Jr. 5] Apr. 9, 1974[54] HEAT TRANSFER PLATES 3,423,079 1/1969 McKeown 263/47 A [76]Inventor: Robert Lee Corbett, Jr., 227 81530 4/196! Menough 263/47 AWestlake Rd., Rocky River, Ohio 441 16 Primary Examiner-John J. CambyAttorney, Agent, or Firm J. H. Slough; Squire, [22] Filed: May 23, 1968Sanders & Dempsey [211 Appl. No.: 731,529 [57] ABSTRACT [52] U S Cl432/260 766/5 B There is disclosed herein a heat transfer plate adapted[51] 1 21/04 to be disposed between coils of metal in an annealing [58]Fieid 266/5 B furnace, the plate comprising a plurality of circumfer- 1432/266 entially spaced bars disposed in two opposing layers, the barsbeing skewed with respect t0 true radii of the [56] References Citedplate whereby the bars of one layer partially overlap UNITED STATESPATENTS the bars of the other layer. 3,145,982 8/1964 Ludwig 263/47 A 16Claims, 7 Drawing Figures HEAT TRANSFER PLATES This invention relates toannealing furnaces for treating coils of metal in strip form and relatesmore particularly to an improved heat transfer plate for transferringheat to and from coils stacked endwise within an annealing furnace.

In known forms of the types of furnaces referred to, the coils of stripmaterial are stacked coaxially upon a suitable base structure having arecirculating fan or blower disposed therein. Each coil defines acentral, coaxial opening or eye, and the fan is adapted to circulate aheated, protective atmosphere gas upwardly around the outside of thecoils and downwardly through the eyes of said coils. Coil separators orconvector plates are provided between adjacent pairs of the stackedcoils, said convector plates spacing the coils from each other andaffording suitable gas passages thus allowing the heated gas tocirculate to the edges of the wraps whereby heat is transferred byconvection and conduction to the interior of the coils. The stackedcoils are preferably enclosed within a gastight inner cover which is, inturn, disposed within a suitable hood or furnace having radiant tubes,burners, or other suitable heating means for heating the inner cover.

The heat transfer plate of this invention is adapted for use as a coilsepartor and convector plate and is further adapted for use as a chargeplate for supporting an entire stack of coils and as a top orifice platefor positioning on top of the uppermost coil. In any of the positionsmentioned, the heat transfer plate of this invention is adapted totransfer heat in an improved manner from the circulating atmosphere gasto the coils, or from the coils to a cooling atmosphere gas, by bothconduction and convection. The heat transfer plae is further constructedin such manner as to provide a controlled turbulence of the atmospheregas adjacent to the edges of the coil wraps whereby more rapid heatingand cooling of the coils is effected resulting in an increase in theoverall efficiency of the furnace.

Coil separators or convector plates of the type referred to aresubjected to substantial load pressures due to the weight of the coilsdisposed thereupon and must be constructed in such manner as towithstand these load pressures while at the same time affording adequategas passages for flow of the heated atmosphere gas to the edges of thecoils. The separators must withstand stresses due to extreme temperaturechanges and provide sufficient supporting area to prevent damage to theedges of the coil wraps. These and many other problems which arise inconnection with manufacture and use of coil separators have been solvedin an improved manner by the heat transfer plate disclosed herein.

It is, therefore, an object of this invention to provide a heat transferplate of improved design providing a venturi effect for causing aturbulent flow of atmosphere gas to the edges of coils and dischargingthe same into the eyes or centers of the coils disposed within anannealing furnace whereby a substantially improved rate of heating andcooling is obtained.

Another object of the invention is to provide a heat transfer platewhich affords adequate areas of contact between support bars of theplate and the coils to more effeciently utilize temperature transfer byconduction as well as by convection in the heating and cooling cycles ofthe furnace.

Another object of this invention is to provide a heat transfer plate asset forth above which is so constructed as to resist distortion due toexpansion and contraction of the metal when subjected to extremetemperature changes.

Still another object of this invention is to provide a heat transferplate having the above features and characteristics wherein thesupporting surface areas are proportioned according to the load weightof the coil diameters and are sufficient to support the coils withoutdamage to the edges of the coil wraps, said plate also affordingadequate circulation of the atmosphere gas across the edges of the coilwraps.

Yet another object of the invention is to provide a heat transfer plateas characterized above which comprises a plurality of like parts soarranged and itnerconnected as to reinforce each other.

A still further object is to' provide a heat transfer plate as set forthabove wherein each of said like parts is secured to at least three otherof said like parts.

Another object of the invention is to provide a heat transfer plate ofthe above type which is of simple, sturdy construction, inexpensive tomanufacture, and highly durable to use.

Still another object of the invention is to provide a heat transferplate of sufficiently sturdy construction whereby it can also be used asa load or charge plate directly on top of the diffuser or furnace basethereby causing additional atmosphere gas to come into contact with thebottom edge of the bottom coil directly from the recirculating fan; thisadditional circulation increases the heating and cooling efficiency ofthe furnace.

Another object of the invention is to provide a heat transfer platewhich allows a crane operator to see through a substantial portion ofthe plate when manipulating the same into position with respect to acoil.

A further object of the invention is to provide a heat transfer platewhich affords increased circulation downwardly through the eyes of thecoils and upwardly around the outside of the coils.

FIG. 2 is a fragmentary transverse section taken generally along theline 22 of FIG. 1;

FIG. 3 is an enlarged detail section taken generally along the line 3-3of FIG. 2;

FIG. 4 is an enlarged plan view of one side of the heat transfer plateof this invention;

FIG. Sis a fragmentary plan view of the opposite side of the heattransfer plate as shown in FIG. 4;

FIG. 6 is a detail section taken along the line 66 of I FIG. 4; and Ilindrical body portion 11 is preferably formed of heavy sheet metal andhas a downwardly projecting, annular flange portion 14 which projectsdownwardly into a granular sealing trough 15 of a generally cup-shapedbase 16. The base 16 has an upwardly projecting, annular flange 17having a slightly larger diameter than the flange portion 14 wherebysaid flange portion is disposed generally within said annular flange 17.The body portion 11 is supported by radially projecting fins 18 thebottom edges of which seat upon the upper edge of the annular flange 17.The base 16 also includes a suitable refractory bottom lining l9 and acentral support structure comprising concentric steel rings 20 havingrefractory material 21 disposed therebetween. An annular plate 22surrounds the concentric rings 20, and a larger annulus 23 is disposedoutwardly therefrom and forms the inner wall of the granular sealingtrough l5. Said trough is filled with a suitable granular sealingmaterial 15', such as sand, into which the flange portion 14 projects.The body portion 11 may also be sealed by mechanical seals of othertypes.

The base 16, as herein illustrated, is securely mounted upon I-beams 24which are seated in a concrete floor 25 or other suitable supportingmeans. A

central cavity 26 in the floor 25 affords space for mounting a motor 27having a shaft 28 which projects upwardly through the central portion ofthe base 16, the upper end of said shaft carrying a centrifugal blower29. The blower 29 is disposed within a central opening 30' of a coilsupport'member or diffuser 30, said support member having upper platemeans 31, generally radially disposed spacers 32, lower plate means 33,and circumferentially disposed, angled dcflectors 34. An atmosphere gasinlet 30a and an atmosphere gas outlet 301; project upwardly through thebase 16 and the lower plate means 33.

As herein illustrated, the coil support member or diffuser 30 supportsfour coils of strip sheet steel stacked vertically'and coaxially withinthe body portion 11 and separated by heat transfer plates 36. Each coil35 defines a central opening or eye 37, and the uppermost of said coilsis provided with a top orifice plate 38 which covers the eye of theupper coil and which may be provided with a central, flow restrictingorifice 39.

An inner cover 40 is disposed over the stacked coils 35, the upper endof said cover being closed by an upper end wall 41 having an upwardlyprojecting lifting bail 41 Said cover has a lower annular base portion42 which seats upon the annular plate 22 and is sealed thereby bygranular sealing means indicated at 42. The inner cover 40 may also besealed by mechanical seals of other types. In the form shown, heatingmeans for the furnace comprise elongated, gas-fired, radiant tubeheaters 43 which are. evenly circumferentially spaced around the outsideof the hood 40 within the refractory lining 13;

The heat transfer plates 36 are identical in form and only one of themwill be herein described in detail. One of the said plates is detailedin FIGS. 3-7, and it will be seen that said plate is substantiallycircular and comprises a plurality of identical bars 44. The bars 44have tapered side edges 44a and 44b and are arranged in layers which forconvenience of designation are generally indicated in FIG. 6 as upperlayer A and lower layer B. Layer A is superimposed over layer B and asbest seen in FIG. 4, the bars 44 of upper layer A are substantiallyangled or skewed with respect to true radii of the heat transfer plate;that is, their outer ends are circumferentially displaced relative totheir inner ends in a counter clockwise direction, whereas the bars ofthe lower layer B are similarly circumferentially skewed the same amountin the opposite or clockwise direction. The inner edges 45 of the barsin layer B overlap the inner edges of the bars in layer A and define acentral opening 46 which is adapted to be disposed coaxially with theeyes 37 of the coils 35 and is somewhat smaller than said eyes. Theouter edges 47 of the bars 44 in layer A overlap the outer edges of thebars in layer B and are disposed generally tangent to a circle having adiameter slightly in excess of the diameter of the coils 35. Thecircumferential spacing and skewing of the bars 44 in each layer is suchthat each bar of each layer overlaps three of the bars in the otherlayer. For example; any bar in the layer A has an outer larger endportion 48 overlapping the outer, larger end portion 48 of a bar in thelayer B, a medial portion 49 similarly overlapping the medial portion 49of another bar in layer B, and a tapered inner end portion 50overlapping the tapered inner end portion 50 of still another bar of thelayer B. In a similar manner, each bar in layer B is attached to atleast three of said bars in layer A. The outer edges of the bars 44 arerounded as indicated at 44' in FIGS. 6-7 adjacent to the upper and lowercoil contacting surfaces of the heat transfer plate 36 to prevent damageto the edges of coil wraps coming in contact therewith. It will befurther noted that the outer edges 47 of the bars 44 as seen in planview (FIGS. 4 and 6) are angled inwardly from rounded apices 47, saidapices defining the outer circumference of the plate 36.

' The means of attachment of the bars 44 is preferably by welding alongthe lateral and end edges of said bars where they cross or overlap asindicated at 51. It will be noted, however, that where the bars cross atthe larger end portions 48, the overlapping bars are not weldedcontinuously throughout the length of their overlapping edges, the weldsbeing confined to two spaced areas indicated at 51a and 51b. Thisenables the bars to expand and contract in response to temperaturechanges without causing the heat transfer plate to distort.

The spaces between the side edges 44a and 44b of the circumferentiallyadjacent bars 44 define inwardly tapering passages 55 for thecirculation of the heated atmosphere gas to the edges of the coil wraps.Thus, the passage means defined by the spaces between said bars are ofsubstantially changing cross sectional area throughout the lengththereof. As will hereinlater become apparent, the direction ofcirculation with respect to the coil separator 36 is generally radiallyinwardly through the spaces between the bars, the inward taper of thepassages 55 providing a venturi effect adjacent to the central opening46. Bars in the upper layer A afford passages which arecircumferentially skewed with respect to the passages provided by thebars in the layer B, and where any two passages cross, generallyindicated at 52, and where they converge at the opening 46, generallyindicated at 53, areas of turbulence are created which increase theheating effiency of the flowing atmosphere gas.

Referring again to FIG. 1 of the drawings, the centrifugal blower 29causes the atmosphere gas to flow radially outwardly below the coils 35at which point the deflectors 34 direct said gas upwardly along theouter surfaces of said coils within the inner cover 40. At the sametime, the blower 29 draws the atmosphere gas downwardly through theconcentric eyes 37 of the coils and the openings 46 in the coilseparators, the top orifice plate 38 restricting such downward flowwhereby a larger portion of the gas is pulled radially inwardly throughthe passages 55 in the heat transfer plates 36 and contributes tocirculation over the edges of the coil wraps.

It will be readily understood that during the heating cycle of theannealing furnace, the heat transfer plates 36, being of smaller massthan the coils 35, will heat or cool more rapidly than said coils.Because the bars 44 are in contact with the edges of the coil wraps,heat is transferred by conduction directly to or from the coils in thearea of contact. The heated atmosphere gas passing through the passages55 between said bars heats the edges of the coil wraps by convection,and it has been found that the turbulence created at 52 (FIG. 4) wherethe passages cross and at 53 where said passages converge substantiallyincreases the convection heating. However, the turbulence is carefullycontrolled to take place within the space between the coils and not inthe area surrounding the coils where it might, for example, disturb thesand sea] at the lower edge of the inner cover 40 and cause the finerparticules of sand to become entrained in the recirculating atmospheregas.

As best seen in FIG. 4, the increased heating at 52 where the 'flowpassages 55 cross is located a substantial distance inwardly from theinner ends of the bars 44 and an even greater distance from the outerends of said bars. Generally, the turbulent area at 52 is adapted to bedisposed substantially one-third of the distance between the innerperiphery of the coil to the outer periphery thereof. It is well-knownin the art of annealing coils of strip metal that the most difficultportion to heat is located horizontally substantially one-third of thedistance between the inner and outer .peripheries of the coil andvertically one-half 'the distance between the edges of the coil wraps.Thus the heat transfer plate of this invention provides for increasedheating by convection in the area most closely adjacent to the portionof the coil which is most difficult to heat.

The inwardly tapering shape of the bars 44 insures that a greatersupporting surface area is provided radially outwardly of the eye of thecoil where the coil wraps are of largest circumference and, therefore,of greatest weight. The outwardly increasing surface area also providesincreased heating by conduction at the outer wraps of the coil where thelarger portion of the mass is located. In the same manner, the outwardlywidening passages 55 between the bars 44 provide a greater flow area forconvection heating of the outer wraps of the coil than of 'the innerwraps thereof. Thus the heat transfer plate'of this inventionisproportioned radially to provide outwardly progressively increasingsupport and heating means which compensate for the outwardlyprogressively increasing weight and mass of the coil wraps. Performancetests have shownthat with the use of heat'transfer plates of this typein a standard annealing furnace, a given charge can be heated insubstantially less time than where prior known types of convector platesor coil separators are used The heat transfer plate 36 of this inventionis readily adaptable for use as a charge plate; that is, a top plate forthe coil support member or diffuser 30. Support members or diffusersvary in form and construction providing various patterns of ribs,.posts, and the like for supporting thestack of coils 35 to be annealedand diffusing atmosphere gas within the inner cover 40. Diffusers arecommonly provided with a solid upper plate disposed upon the ribs orposts for receiving the stack of coils. This construction does notafford means for the atmosphere gas to circulate across the lower edgesof the wraps of the lowermost coil, and it is well known that the lowercoil is the slowest coil to heat due to the lack of circulation underthis coil.

By varying the number and the size of bars 44 in a heat transfer plate36, said plate can be adapted to seat upon any pattern of diffuser ribsor posts thereby adapting it for 'use as a charge support plate directlyabove the diffuser and allowing combined convection and conductionheating at the lower edges of the lowermost coil wraps. The controlledturbulence action discussed above is thus provided at the bottom of thestack of coils as well as between adjacent coils.

It will be further noted that a heat transfer plate of the type shown at36 may be used at the top of the stack of coils 35 in place of the toporifice plate 38. This provides for convection heating at the upper edgeof the uppermost coil, it being understood that the central opening 46can be varied in size depending upon the length of the bars 44 to affordthe desired restriction at this point.

In the specification and claims of the present application, it will beunderstood that heat transfer plate or similar terminology refers to theinvention as set forth herein whether the same is used as a coilspearator, charge plate, or top orifice plate.

An important advantage of the heat transfer plate of the presentinvention is that it allows a relatively unrestricted flow 7 of theatmosphere gas downwardly through the aligned eyes 37 of the stackedcoils. The central opening 46 is necessarily smaller than the eyes 37 toprovide adequate support for the inner coil wraps and prevent said innerwraps from falling or being drawn downwardly through said eyes by thecirculating gas. Because only the inner smaller ends of the bars 44project inwardly of the eyes 37, the gas flows through the spacesbetween said inner ends and is thereby provided with substantially moreunrestricted cross sectional flow area than known coil separators.

It will be further noted that the outer ends of the bars 44 similarlyafford a relatively unrestricted flow of the atmosphere gas upwardlyaround the outside of the coils between said coils and the inner cover40. The heat transfer plates 36 are usually made for maximum diametercoils but are frequently'used with smaller diameter coils whereby thebars 44 extend radially outwardly beyond the coils 35 a substantialdistance. Because of the bar construction of the present invention, onlythe outer end portions of the bars project into the upward flow ofatmosphere gas thereby affording a relatively unrestricted flow patharound'the outside of the coils.

Another important advantage of the heat transfer plate of the presentinvention is its see-through feature. Convector plates now widely usedin the annealing art are commonly provided with solid plates eitherdisposed on top of a plurality of radially disposed ribs or sandwichedbetween layers or ribs. These plates have only a central aperture toallow return flow ofthe atmosphere gas. Manipulation of the convectorplates is usually by means of a crane operated by a workman disposed asubstantial distance from the furnace. in placing the'convectorplatesupon the coils of steel, the operator should avoid damaging thecoil wraps because bent or damaged wraps present problems at the temperI mill. The construction of the heat transfer plate of the presentinvention allows the operator to see through a substantial portion ofthe plate thereby greatly aiding him in th difficult task of accuratelyplacing the plate in position with respect to a coil by use of a crane.

The inner cover 40 is also lowered into position over the stacked coilsby means of a crane. This inevitably causes the inner cover to swing asit is lowered whereby it hits the outer peripheral edges of theconvector plates. The inner cover also tends to hang up on the edges ofthe plates when the cover is being removed. The resultcan beconsiderabledamage to the inner cover. The heat tranfer plate of thepresent invention greatly reduces damage of the aforesaid type byproviding the outer ends of the bars 44 with the rounded apices 47a.Since the apicesdefine the largest diameter of the heat transfer'plate36, onlyvthese roundedportions actually contact the inner cover therebyreducing friction andeliminating long edges or sharp corners upon whichthe inner cover can hang up or against which it can swing.

An additional advantage of the present construction is that it providesgas passagesof full height without sacrificing stacking height. Asmentioned above, convector plates now commonly used throughout theannealing industry include cover plates or cente plates sandwichedbetween radial bars which said plates provide an obstruction andfrictional loss to the flow of gas between the stacked coils. The resultis that in order to provide gas passages of a given height, the totalthickness of each convector plate must be increased by the thickness ofthe cover or center plate. The present invention eliminates thisadditional plate and thereby reduces the overall thickness of theconvector plate.

The significance of the last mentioned feature of the presentinvention-will become clear from the following example: on a typicalannealing floor using 117 stools or bases, approximately 350 convectorplates are in use during the annealing of the coils. if the added coveror center plate in each convector plate is a minimal /4 inch thick,there is a total loss in stacking height of 87 b inch per charge or theequivalent of more than two 41 inch wide coils. A 41 inch coil having adiameter of 72 inches weighs approximately 40,000 lbs. whereby the totalloss of annealing capacity for each charge would be 80,000 lbs. Aconservative estimate is that there could be a saving of at least 8million lbs. of annealing capacity per year on an annealing floor as setforth above by using the heat transfer plates of the present inventionrather than conventional convector plates.

in some instances, coils of substantially greater width than thoseherein illustrated are annealed in a furnace of the type shown. Theresult is that fewer coils are stacked in a given furnace whereby fewerconvector plates are normally used. However, reducing the number ofconvector plates also reduces the flow of atmosphere gas between thecoils thereby reducing the heating and cooling efficiency. The fullcirculation capacity of the blower 29 may not be fully utilized if theflow between the coils is thus restricted. This problem can be solvedwith theheat transfer plates of the present invention by stacking two ormore of said plates between adjacent coils to match the flow capacitybetween the coils with the circulation capacity of the blower. The bars44 are so angled that when one plate is disposed upon another, theadjacent layers of bars are always disposed at an angle to each otherfor maximum support.

The load supporting bars 44 of the present invention preferably providea total direct contact supporting surface area of about percent of thetotal area of the heat transfer plate 36. This may be varied somewhat byvarying the width of the bars, depending upon the gage of the stripmetal comprising the coils 35. Heavier gage metals generally need lesssupporting surface than the lighter gage metals whereby the bars can benarrower and the spaces therebetween wider. Generally, it is preferredthat the bars provide a supporting surface area of from 40 to percent ofthe total coil area, the higher percentages being preferable forrelatively lighter gage metals.

From the foregoing it will be readily seen that the heat transfer plateof this invention comprises, first of all, a sturdy structure capable ofsupporting almost unlimited weight. This is due to the layeredconstruction in which the bars are disposed flatwise one above the.

other whereby the pressure which the plate can withstand is limited onlyby the quality or quantity of material from which it is made. Bydisposing the bars flatwise, and providing the rounded corners 44',adequate supporting surface area is provided for each coil with-' outdamage to the edges of the coil wraps. It will be further noted that thespaces between the adjacent bars 44 provide not only adequate flow areafor-the atmosphere gas but also a pattern of criss-cross passages whichcauses a turbulence of the atmosphere gas thereby accelerating theheating arid cooling of the coils. The overlapping construction in whicheach bar is firmly connected to at least three other bars affords astructure which effectively resists distortion due to the extremetemperature changes and loads to which the bars are subjected. The factthat the entire coil separator is constructed of a multiplicity of likeparts effects great savings in cost of construction and, because of itssimplicity, provides a coil separator which is highly durable in use.The present construction provides complete through openings betweenadjacent coils whereby the heated gas flows freely across the edges ofthe coil wraps. A middle plate of the type found in some prior artdevices disposed between the bars is not necessary in this design forconnecting the bars together with the result that there is less metal toheat and load or charge piling height is increased within the furnace.it will be further noted that the heat transfer plate disclosed hereinis reversible, the relative positions of the bars and passages being thesame no matter which side is disposed upwardly, and that said plate maybe used either singly or in multiples.

it will be understood that many changes in the details of the inventionas herein described and illustrated may be made without, however,departing from the spirit thereof or the scope of the appended claims.

W at Qla mi in at least two layers with one layer being superimposedupon the other layer; at least certain of said bars beingcircumferentially spaced from each other and providing gas flow passagestherebetween; said certain bars being skewed with respect to true radiiof said plate and having inner end portions disposed adjacent to theaxis of said plate and outer end portions disposed at the outerperiphery of said plate; the inner and outer end portions ofieach saidcertain bar in each layer overlapping and being secured to the inner andouter end portions, respectively, of two other bars in the other saidlayer.

2. A heat transfer plate as set forth in claim 1: said inner ends of atleast some of said bars defining a central opening and the spacingbetween said certain bars defining passages extending from the outerperiphery of said plate to said central opening.

3. A heat transfer plate as set forth in claim 2: said certain barsbeing substantially flat with the overlapping portions of said certainbars being in flatwise contact with the bars to which they are secured.

4. A heat transfer plate as set forth in claim 2: each said certain barin each said layer having portions overlapping portions of three bars insaid other layer; circumferentially adjacent bars in each said layerdefining passages therebetween which cross over and are open to passagesof the other said layer whereby a turbulence is produced in the flowinggas at the intersecting passages.

5. A heat transfer plate as set forth in claim 4: said bars and saidpassages tapering inwardly from the outer edge of said plate to saidcentral opening.

6. A heat transfer plate as set forth in claim 5: each said bar of eachsaid layer having a medial portion overlapping the medial portion of abar in said other layer.

7. A heat transfer plate for spacing coils of metal stacked coaxiallywithin a furnace, said heat transfer plate comprising two contiguouslayers of flat metal bars of substantially uniform length disposed abouta vertical axis and circumferentially spaced from each other in eachlayer; the inner ends of said bars defining a substantially circularcentral opening about said axis whereby said bars form a flat, annularstructure; the bars in one of said layers being skewed with respect totrue radii of the plate in one circumferential direction and the bars inthe other of said layers being skewed with respect to said radii a likeamount in the opposite circumferential direction; each said bar in eachsaid layer having an outer end portion overlapping and welded to theouter end portion of a first bar in said other layer, a medial portionoverlapping and welded to a medial portion of a second bar in said otherlayer, and an inner end portion overlapping and welded to the inner endportion of a third bar of said other layer; circumferentially adjacentbars in each said layer defining passages therebetween, each of whichsaid passages crosses over and is open to passages of the other saidlayer.

8. A heat transfer plate as set 'forth in claim 7: said outer endportion of each said bar having side edge portions thereof disposeddiagonally across said first bar of said other layer; said side edgeportions being welded to said first bar only at spaced areas to allowseparate expansion and contraction of the bars due to temperaturechanges.

9. A heat transfer plate for spacing coils' of metal stacked coaxiallywithin a furnace, said heat transfer plate comprising two contiguouslayers-of flat metal bars of substantially uniform length disposed abouta vertical axis and circumferentially spaced'from each other in eachlayer; the inner ends of said bars defining a substantially circularcentral opening about said axis whereby said bars form a flat, annularstructure; the bars in one of said layers being skewed with respecttotrue radii of the plate in one circumferential direction and the bars inthe other of said layers being skewed with respect to said radii a likeamount in the opposite circumferential direction; each said bar in eachsaid layer having an outer end portion overlapping and welded to theouter end portion of a first bar in said other layer, a medial portionoverlapping and welded to a medial portion of a second bar in said otherlayer, and an inner end portion overlapping and welded to the inner endportion of a third bar of said other layer; circumferentially adjacentbars in each said layer defining passages therebetween, each of whichsaid passages crosses over and is open to passages of the other saidlayer; said outer end portion of each said bar having side edge portionsthereof disposed diagonally across said first bar of said other layer;said side edge portions being welded to said first bar only at spacedareas to allow separate expansion and contraction of the bars due totemperature changes; the upwardly and downwardly facing, coil contactingsurfaces of each said bar being rounded along the perimeter thereof toprevent damage to the edges of the coil wraps.

10. A heat transfer member for transferring heat by both conduction andconvection to the coil wrap edges of strip metal coils stacked coaxiallywithin an annealing furnace, said member comprising contiguous layers offlat metal bars of substantially uniform shape disposed about a verticalaxis and uniformly circmferentially spaced from each other in eachlayer; said bars tapering inwardly, the inner ends thereof defining acircular central opening whereby said bars form a generally flat,annular structure; said bars being substantially skewed with respect tothe true radii of said member, the bars in one of said layers beingskewed in one circumferential direction and the bars in the other ofsaid layers being skewed the same amount in the opposite circumferentialdirection; each said bar in each said layer having its outer, larger endportion overlapping and secured to the outer end portion of one bar inthe other layer and its inner, smaller end portion overlapping andsecured to the inner end portion of another bar of said other layer;circumferentially adjacent bars in each layer defining inwardly taperedpassages for directing a circulating atmosphere gas across the edges ofthe coil wraps, each said passage crossing over and being open to apassage of the other said layer whereby a turbulence is produced in theflowing gas at the intersection of said passages adjacent to the edgesof the coil wraps when said member is disposed coaxially against an endof a coil, said bars and said passages providing outwardly increasingareas of support, heat conduction, and gas flow whereby said member isradially proportioned with respect to the outwardly increasing largercoil wraps and coil mass.

11. A heat transfer turbulator member as set forth in claim 10: eachsaid bar having a medial portion thereof overlapping and secured to amedial portion of still another bar of said other layer; and each saidpassage in each layer crossing over and being open to three passages ofsaid other layer.

12. A heat transfer member for transferring heat by both conduction andconvection to the coil wrap edges of strip metal coils stacked coaxiallywithin an annealing furnace, said member comprising contiguous layers offlat metal bars of substantially uniform shape disposed about a verticalaxis and uniformly circumferentially spaced from each other in eachlayer; said bars tapering inwardly, the inner ends thereof defining acir' cular central opening whereby said bars form a generally flat,annular structure; said bars being substantially skewed with respect tothe true radii of said member, the bars in one of said layers beingskewed in one circumferential direction and the bars in the other ofsaid layers being skewed the same amount in the opposite circumferentialdirection; each said bar in each said layer having its outer, larger endportion overlapping and secured to the outer end portion of one bar inthe other layer and its inner, smaller end portion overlapping andsecured to the inner end portion of another bar vof said other layer;circumferentially adjacent bars in each layer defining inwardly taperedpassages for dia turbulence is produced in the flowing gas at theinterupon the other layer; said bars being circumferentially spaced fromeach other and providing gas flow passages therebetween; said bars beingskewed with 'respect to true radii of said plate and having inner endportions disposed adjacent to the axis of said plate and I outer endportions disposed at the outer periphery of said plate; each said bar ineach said layer having porsection of said passages adjacent to the edgesof the coil wraps when said member is disposed coaxially against an endof a coil, said bars and said passages providing outwardly increasingareas of support, heat conduction, and gas flow whereby said member isradially proends of the bars in one of said layers extending radiallyoutwardly beyond the outer ends of the bars in the other layer and theinner ends of the bars in said other layer extending radially inwardlybeyond the inner ends of the bars in said one layer.

13. A heat. transfer turbulator member as set forth in claim 12: eachsaid bar being welded to the bars it overlaps along overlapping side andend edge portions thereof to provide a unified structure. v

14. A heat transfer plate for transferring heat to coils of metalstacked coaxially within a furnace and directing a flow of atmospheregas across the edges of the coil wraps, said plate comprising aplurality of horizontal bars disposed about a vertical axis, said barsarranged in at least two layers with one layer being superimposed tionsoverlapping portions of three bars in said other layer;circumferentially adjacent bars in each said layer defining passagestherebetween which cross over and are open to passages of the other saidlayer whereby a turbulence is produced in the flowing gas at theintersections of said passages; said passages providing a plu rality ofcross-over areas circumferentially spaced around said plate inwardly ofthe inner ends of said bars in such position as to be disposedsubstantially onethird the distance between the inner and outerperipheries of a coil positioned upon said plate.

15. A convector plate for use between two stacked coils of sheet metalduring annealing of the latter, said plate comprising two superimposedrib systems, each composed of a plurality of separate ribs arranged sothat the ribs and the passages between the ribs together define anannulus, each rib, being generally wedgeshaped in plan, and havingstraight edges which extend between the inner and outer peripheries ofsuch annulus and are inclined in the same sense to the radii of theannulus, characterized in that the ribs of each system have their outerends substantially coinciding with the outer ends of the ribs of theother system, but are inclined to the radii of the annulus in asense.opposite to the sense in which the ribs of the other system areinclined to the radii of the annulus, and in that the rib systems areconstructed so that air drawn inward along the convector plate towardthe interior of the coils is separated into two sets of streams, oneflowing through the passages between the ribs of one system and theother flowing through the passages between the ribs of the other system,the outer portion of each passage of one rib system, adjacent theperiphery of the convector plate, being merged with a passage of theother rib system, and most of the remainder of each passage beingseparated from the passages of the other rib system to minimizeinterference between the flow through the remainder of each passage andthe flow through the passages of the other rib system.

16; A convector plate according to claim 15 wherein the two rib systemsare directly secured to one another, and each rib of one system overliesnot more than four ribs of the other system.

UNITED STATES PATENT OFFICE CERTW!(I/\TE OF (IURREC'IION Patent No. 3802 834 Dated April 1974 Robert L. Corbett, Jr. Inventor(s) It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 1, line 27, "separtor" should read separator line 35, "plae"should read plate Column 2, line 16,

i "itnercon" should read intercQ filine 49, "spearated" should readseparated Column 4, line 64,"effiency" should read efficiency, Column 5,line 65', after. the word "used" insert a period[.). Column 6, line 32"spearator" should read separator line 66, "or", second occurrence,should read of Column 7, line 9, "th" should read" the line 18, traner"should read transfer line 3 1, "c,ente" should I read center Claim 1,column 9, line 8, delete "in each layer"; Claim 4, column 9, line 22,"delete "in each said layer";

1 Column 10, line 35, "circmferen-" should read circumferen Signed andsealed this 1st day of October 1974.

(SEAL) Attest:

MCCOY i'i. GIBdON JR. C. MaRSkLiL DANN Attesting Officer Commissioner ofPatents OQM P04051 (O-69) USCOMM-DC 60376-P69 u.s. GOVERNMENT PRINTINGOFFICE: 930

1. A heat transfer plate for transferring heat to coils of metal stackedcoaxially within a furnace and directing a flow of atmosphere gas acrossthe edges of the coil wraps, said plate comprising a plurality ofhorizontal bars disposed about a vertical axis, said bars arranged in atleast two layers with one layer being superimposed upon the other layer;at least certain of said bars being circumferentially spaced from eachother and providing gas flow passages therebetween; said certain barsbeing skewed with respect to true radii of said plate and having innerend portions disposed adjacent to the axis of said plate and outer endportions disposed at the outer periphery of said plate; the inner andouter end portions of each said certain bar in each layer overlappingand being secured to the inner and outer end portions, respectively, oftwo other bars in the other said layer.
 2. A heat transfer plate as setforth in claim 1: said inner ends of at least some of said bars defininga central opening and the spacing between said certain bars definingpassages extending from the outer periphery of said plate to saidcentral opening.
 3. A heat transfer plate as set forth in claim 2: saidcertain bars being substantially flat with the overlapping portions ofsaid certain bars being in flatwise contact with the bars to which theyare secured.
 4. A heat transfer plate as set forth in claim 2: each saidcertain bar in each said layer having portions overlapping portions ofthree bars in said other layer; circumferentially adjacent bars in eachsaid layer defining passages therebetween which cross over and are opento passages of the other said layer whereby a turbulence is produced inthe flowing gas at the intersecting passages.
 5. A heat transfer plateas set forth in claim 4: said bars and said passages tapering inwardlyfrom the outer edge of said plate to said central opening.
 6. A heattransfer plate as set forth in claim 5: each said bar of each said layerhaving a medial portion overlapping the medial portion of a bar in saidother layer.
 7. A heat transfer plate for spacing coils of metal stackedcoaxially within a furnace, said heat transfer plate comprising twocontiguous layers of flat metal bars of substantially uniform lengthdisposed about a vertical axis and circumferentially spaced from eachother in each layer; the inner ends of said bars defining asubstantially circular central opening about said axis whereby said barsform a flat, annular structure; the bars in one of said layers beingskewed with respect to true radii of the plate in one circumferentialdirection and the bars in the other of said layers being skewed withrespect to said radii a like amount in the opposite circumferentialdirection; each said bar in each said layer having an outer end portionoverlapping and welded to the outer end portion of a first bar in saidother layer, a medial portion overlapping and welded to a medial portionof a second bar in said other layer, and an inner end portionoverlapping and welded to the inner end portion of a third bar of saidother layer; circumferentially adjacent bars in each said layer definingpassages therebetween, each of which said passages crosses over and isopen to passages of the other said layer.
 8. A heat transfer plate asset forth in claim 7: said outer end portion of each said bar havingside edge portions thereof disposed diagonally across said first bar ofsaid other layer; said side edge portions being welded to said first baronly at spaced areas to allow separate expansion and contraction of thebars due to temperature changes.
 9. A heat transfer plate for spacingcoils of metal stacked coaxially within a furnace, said heat transferplate comprising two contiguous layers of flat metal bars ofsubstantially uniform length disposed about a vertical axis andcircumferentially spaced from each other in each layer; the inner endsof said bars defining a substantially circular central opening aboutsaid axis whereby said bars form a flat, annular structure; the bars inone of said layers being skewed with respect to true radii of the platein one circumferential direction and the bars in the other of saidlayers being skewed with respect to said radii a like amount in theopposite circumferential direction; each said bar in each said layerhaving an outer end portion overlapping and welded to the outer endportion of a first bar in said other layer, a medial portion overlappingand welded to a medial portion of a second bar in said other layer, andan inner end portion overlapping and welded to the inner end portion ofa third bar of said other layer; circumferentially adjacent bars in eachsaid layer defining passages therebetween, each of which said passagescrosses over and is open to passages of the other said layer; said outerend portion of each said bar having side edge portions thereof disposeddiagonally across said first bar of said other layer; said side edgeportions being welded to said first bar only at spaced areas to allowseparate expansion and contraction of the bars due to temperaturechanges; the upwardly and downwardly facing, coil contacting surfaces ofeach said bar being rounded along the perimeter thereof to preventdamage to the edges of the coil wraps.
 10. A heat transfer member fortransferring heat by both conduction and convection to the coil wrapedges of strip metal coils stacked coaxially within an annealingfurnace, said member comprising contiguous layers of flat metal bars ofsubstantially uniform shape disposed about a vertical axis and uniformlycircumferentially spaced from each other in each layer; said barstapering inwardly, the inner ends thereof defining a circular centralopening whereby said bars form a generally flat, annular structure; saidbars being substantially skewed with respect to the true radii of saidmember, the bars in one of said layers being skewed in onecircumferential direction and the bars in the other of said layers beingskewed the same amount in the opposite circumferential direction; eachsaid bar in each said layer having its outer, larger end portionoverlapping and secured to the outer end portion of one bar in the otherlayer and its inner, smaller end portion overlapping and secured to theinner end portion of another bar of said other layer; circumferentiallyadjacent bars in each layer defining inwardly tapered passages fordirecting a circulating atmosphere gas across the edges of the coilwraps, each said passage crossing over and being open to a passage ofthe other said layer whereby a turbulence is produced in the flowing gasat the intersection of said passages adjacent to the edges of the coilwraps when said member is disposed coaxially against an end of a coil,said bars and said passages providing outwardly increasing areas ofsupport, heat conduction, and gas flow whereby said member is radiallyproportioned with respect to the outwardly increasing larger coil wrapsand coil mass.
 11. A heat transfer turbulator member as set forth inclaim 10: each said bar having a medial portion thereof overlapping andsecured to a medial portion of still another bar of said other layer;and each said passage in each layer crossing over and being open tothree passages of said other layer.
 12. A heat transfer member fortransferring Heat by both conduction and convection to the coil wrapedges of strip metal coils stacked coaxially within an annealingfurnace, said member comprising contiguous layers of flat metal bars ofsubstantially uniform shape disposed about a vertical axis and uniformlycircumferentially spaced from each other in each layer; said barstapering inwardly, the inner ends thereof defining a circular centralopening whereby said bars form a generally flat, annular structure; saidbars being substantially skewed with respect to the true radii of saidmember, the bars in one of said layers being skewed in onecircumferential direction and the bars in the other of said layers beingskewed the same amount in the opposite circumferential direction; eachsaid bar in each said layer having its outer, larger end portionoverlapping and secured to the outer end portion of one bar in the otherlayer and its inner, smaller end portion overlapping and secured to theinner end portion of another bar of said other layer; circumferentiallyadjacent bars in each layer defining inwardly tapered passages fordirecting a circulating atmosphere gas across the edges of the coilwraps, each said passage crossing over and being open to a passage ofthe other said layer whereby a turbulence is produced in the flowing gasat the intersection of said passages adjacent to the edges of the coilwraps when said member is disposed coaxially against an end of a coil,said bars and said passages providing outwardly increasing areas ofsupport, heat conduction, and gas flow whereby said member is radiallyproportioned with respect to the outwardly increasing larger coil wrapsand coil mass; each said bar having a medial portion thereof overlappingand secured to a medial portion of still another bar of said otherlayer; each said passage in each layer crossing over and being open tothree passages of said other layer; the outer ends of the bars in one ofsaid layers extending radially outwardly beyond the outer ends of thebars in the other layer and the inner ends of the bars in said otherlayer extending radially inwardly beyond the inner ends of the bars insaid one layer.
 13. A heat transfer turbulator member as set forth inclaim 12: each said bar being welded to the bars it overlaps alongoverlapping side and end edge portions thereof to provide a unifiedstructure.
 14. A heat transfer plate for transferring heat to coils ofmetal stacked coaxially within a furnace and directing a flow ofatmosphere gas across the edges of the coil wraps, said plate comprisinga plurality of horizontal bars disposed about a vertical axis, said barsarranged in at least two layers with one layer being superimposed uponthe other layer; said bars being circumferentially spaced from eachother and providing gas flow passages therebetween; said bars beingskewed with respect to true radii of said plate and having inner endportions disposed adjacent to the axis of said plate and outer endportions disposed at the outer periphery of said plate; each said bar ineach said layer having portions overlapping portions of three bars insaid other layer; circumferentially adjacent bars in each said layerdefining passages therebetween which cross over and are open to passagesof the other said layer whereby a turbulence is produced in the flowinggas at the intersections of said passages; said passages providing aplurality of cross-over areas circumferentially spaced around said plateinwardly of the inner ends of said bars in such position as to bedisposed substantially one-third the distance between the inner andouter peripheries of a coil positioned upon said plate.
 15. A convectorplate for use between two stacked coils of sheet metal during annealingof the latter, said plate comprising two superimposed rib systems, eachcomposed of a plurality of separate ribs arranged so that the ribs andthe passages between the ribs together define an annulus, each rib beinggenerally wedge-shaped in plan, and having straight edges whiCh extendbetween the inner and outer peripheries of such annulus and are inclinedin the same sense to the radii of the annulus, characterized in that theribs of each system have their outer ends substantially coinciding withthe outer ends of the ribs of the other system, but are inclined to theradii of the annulus in a sense opposite to the sense in which the ribsof the other system are inclined to the radii of the annulus, and inthat the rib systems are constructed so that air drawn inward along theconvector plate toward the interior of the coils is separated into twosets of streams, one flowing through the passages between the ribs ofone system and the other flowing through the passages between the ribsof the other system, the outer portion of each passage of one ribsystem, adjacent the periphery of the convector plate, being merged witha passage of the other rib system, and most of the remainder of eachpassage being separated from the passages of the other rib system tominimize interference between the flow through the remainder of eachpassage and the flow through the passages of the other rib system.
 16. Aconvector plate according to claim 15 wherein the two rib systems aredirectly secured to one another, and each rib of one system overlies notmore than four ribs of the other system.